Automatic wound coupling detection in negative pressure wound therapy systems

ABSTRACT

Embodiments of negative pressure wound therapy systems and methods for operating the systems are disclosed. In some embodiments, a system includes a negative pressure source, a sensor, and a controller. The negative pressure source can provide negative pressure via a fluid flow path to the wound dressing. The sensor can monitor pressure in the fluid flow path. The controller can determine whether the wound dressing is coupled to a wound from a change in magnitude of pressure in the fluid flow path over time being more indicative of a steady state condition than a chaotic condition while the negative pressure source maintains negative pressure in the fluid flow path within a pressure range. In addition, the controller can output a first indication denoting that the wound dressing is coupled to the wound and a second indication denoting that the wound dressing is not coupled to the wound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of International PatentApplication No. PCT/US2017/032545, filed May 12, 2017, which claims thebenefit of U.S. Provisional Application No. 62/335,978, filed May 13,2016, and U.S. Provisional Application No. 62/378,856, filed Aug. 24,2016; the disclosures of which are hereby incorporated by reference intheir entirety.

BACKGROUND

Embodiments of the present disclosure relate to methods and apparatusesfor dressing and treating a wound with negative or reduced pressuretherapy or topical negative pressure (TNP) therapy. In particular, butwithout limitation, embodiments disclosed herein relate to negativepressure therapy devices, methods for controlling the operation of TNPsystems, and methods of using TNP systems.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described hereinafter,by way of example only, with reference to the accompanying drawings inwhich:

FIG. 1 illustrates a negative pressure wound therapy system according tosome embodiments.

FIGS. 2A, 2B, and 2C illustrate a pump assembly and canister accordingto some embodiments.

FIGS. 3A, 3B, 3C, 3D, 3E, 3F, and 3G illustrate components of a negativepressure therapy system according to some embodiments.

FIG. 4 illustrates components of a negative pressure therapy system thatincludes multiple sensors according to some embodiments.

FIG. 5 illustrates a wound coupling detection process according to someembodiments.

FIGS. 6 and 7 illustrate example pressure versus time curves for anegative pressure therapy system according to some embodiments.

FIGS. 8, 9, and 10 illustrate variations due to a gas leak, change influid rate, and change in vacuum level according to some embodiments.

SUMMARY

In some embodiments, an apparatus for applying negative pressure to awound is disclosed. The apparatus can include: a negative pressuresource configured to couple via a fluid flow path to a wound dressingand provide negative pressure to the wound dressing; a sensor configuredto monitor pressure in the fluid flow path; and a controller configuredto: determine that the wound dressing is coupled to a wound from achange in a magnitude of pressure in the fluid flow path over a timeduration being indicative of a steady state condition while the negativepressure source maintains negative pressure in the fluid flow pathwithin a target pressure range, output a first indication denoting thatthe wound dressing is coupled to the wound, determine that the wounddressing is not coupled to the wound from the change in the magnitude ofpressure in the fluid flow path over the time duration being indicativeof a chaotic condition while the negative pressure source maintainsnegative pressure in the fluid flow path within the target pressurerange, and output a second indication different from the firstindication denoting that the wound dressing is not coupled to the wound.

The apparatus of the preceding paragraph can include one or more of thefollowing features: The controller is further configured to: in responseto the determination that the wound dressing is coupled to the wound,store, in a memory device, device usage data indicating a compliant useof the negative pressure source. The controller is further configuredto: in response to the determination that the wound dressing is notcoupled to the wound, store, in a memory device, device usage dataindicating a misuse use of the negative pressure source. The deviceusage data comprises one or more of a pressure level, an alarm, anexudate level, an event log, or a therapy duration. The controller isfurther configured to compare a measure of irregularity of the change inthe magnitude over the time duration to a threshold to determine whetherthe change in the magnitude over the time duration is indicative of thesteady state condition. The measure of irregularity is responsive to thechange in the magnitude over the time duration of at least 1 second, 10seconds, 30 seconds, 1 minute, or 5 minutes. The controller is furtherconfigured to: perform a statistical operation, a trending operation, afiltering operation, a cumulative summation operation, or a low-passfiltering operation on the magnitude over the time duration to generatean output value; and determine that the change in the magnitude over thetime duration is indicative of the steady state condition in response toa determination that the output value is indicative of the steady statecondition. The controller is configured to determine that the change inthe magnitude over the time duration is indicative of the steady statecondition from a time domain representation of the magnitude over thetime duration and a frequency domain representation of the magnitudeover the time duration. The controller is further configured to comparethe magnitude over the time duration to a pressure pattern to determinewhether the change in the magnitude over the time duration is indicativeof the steady state condition. The pressure pattern is indicative ofpressure in the fluid flow path when the wound dressing is coupled tothe wound while the negative pressure source maintains negative pressurein the fluid flow path within the target pressure range. The pressurepattern is indicative of pressure in the fluid flow path when the wounddressing is not coupled to the wound while the negative pressure sourcemaintains negative pressure in the fluid flow path within the targetpressure range. The first indication denotes a compliant use of thenegative pressure source, and the second indication denotes anon-compliant use of the negative pressure source. The controller isfurther configured to: output the first indication for storage in amemory device, or output the second indication for storage in the memorydevice. The controller is further configured to: output the firstindication by causing a transmitter to transmit the first indication toa computing device via a communication network, or output the secondindication by causing the transmitter to transmit the second indicationto the computing device via the communication network. The controller isfurther configured to: output the first indication for presentation to auser, or output the second indication for presentation to the user. Thefluid flow path comprises at least one lumen. The fluid flow pathcomprises a plurality of lumens. The controller is configured toactivate and deactivate the negative pressure source responsive to thefirst indication or the second indication. The negative pressure sourceis configured to perform negative pressure therapy when the magnitudeover the time duration is maintained within the target pressure range.

In some embodiments, a method of operating a negative pressure woundtherapy apparatus is disclosed. The method can include: providingnegative pressure to a wound dressing via a fluid flow path using anegative pressure source; monitoring with a sensor pressure in the fluidflow path; determining whether the wound dressing is coupled to a woundfrom a change in a magnitude of pressure in the fluid flow path over atime duration being indicative of a steady state condition whilemaintaining negative pressure in the fluid flow path within a targetpressure range; in response to determining that the wound dressing iscoupled to the wound from the change in the magnitude over the timeduration, outputting a first indication denoting that the wound dressingis coupled to the wound; and in response to determining that the wounddressing is not coupled to the wound from the change in the magnitudeover the time duration, outputting a second indication different fromthe first indication denoting that the wound dressing is not coupled tothe wound.

The method of the preceding paragraph can include one or more of thefollowing features: The method can further include storing, in a memorydevice, device usage data associated with a compliant use of thenegative pressure wound therapy apparatus in response to determining thewound dressing is coupled to the wound. The method can further includestoring, in a memory device, device usage data associated with a misuseuse of the negative pressure wound therapy apparatus in response todetermining the wound dressing is not coupled to the wound. The deviceusage data comprises one or more of a pressure level, an alarm, anexudate level, an event log, or a therapy duration. Said determiningcomprises comparing a measure of irregularity of the change in themagnitude over the time duration to a threshold. The measure ofirregularity is responsive to the change in the magnitude over the timeduration of at least 1 second, 10 seconds, 30 seconds, 1 minute, or 5minutes. The method can further include performing a statisticaloperation, a trending operation, a filtering operation, a cumulativesummation operation, or a low-pass filtering operation on the magnitudeover time to generate an output value, wherein said determiningcomprises determining whether the change in the magnitude over the timeduration is indicative of the steady state condition in response todetermining that the output value is indicative of the steady statecondition. The method can further include comparing the magnitude overthe time duration to a pressure pattern to determine whether the changein the magnitude over the time duration is indicative of the steadystate condition.

In some embodiments, an apparatus for applying negative pressure to awound is disclosed. The apparatus comprising: a negative pressure sourceconfigured to couple via a fluid flow path to a wound dressing andprovide negative pressure to the wound dressing; a sensor configured tomonitor pressure in the fluid flow path; and a controller configured to:based at least in part on the pressure in the fluid flow path, determinethat the wound dressing is coupled to a wound based on at least one ofdetection of change in flow of gas in the fluid flow path, detection ofchange in flow of exudate in the fluid flow path, change in vacuum levelif the fluid flow path, or detection of presence of blood in the fluidflow path, and output an indication that the wound dressing is coupledto the wound.

The apparatus of the preceding paragraph can include one or more of thefollowing features: The controller is configured to determine that thewound dressing is coupled to the wound further based on an activitylevel of the negative pressure source. The negative pressure sourcecomprises a pump operated by an actuator, and wherein the activity levelcomprises at least one of a pump speed, a pulse width modulation (PWM)signal configured to drive the actuator, or a current signal configuredto drive the actuator. The controller is configured to determine a firstindicator associated with change in the activity level over a timeduration. The first indicator comprises a statistical indicator. Thecontroller is further configured to perform a time series analysis todetermine if the first indicator deviates from a first threshold and inresponse to a determination that the first indicator deviates from thefirst threshold, determine that the wound dressing is coupled to thewound. The time series analysis comprises determination of a cumulativesum (Cusum) of the first indicator. The Cusum of the first indicatorscomprises a non-causal Cusum, sliding causal Cusum, or cumulative causalCusum. The first indicator comprises kurtosis of standard deviation ofthe activity level, and wherein the first indicator is indicative of achange in flow of exudate in the fluid flow path. The controller isfurther configured to determine a cumulative sum (Cusum) of secondindicator associated with change in the activity level over the timeduration, the second indicator different from the first indicator. Thesecond indicator comprises standard deviation of the activity levelindicative of a change in a gas leak rate in the fluid flow path, andthe controller is further configured to determine if the secondindicator deviates from a second threshold and in response to adetermination that the second indicator deviates from the secondthreshold, determine that the wound dressing is coupled to the wound.The controller is further configured to determine a cumulative sum(Cusum) of third indicator associated with change in the pressure in thefluid flow path over the time duration, the third indicator differentfrom the first and second indicators. The third indicator comprises meanpressure in the fluid flow path indicative of a change in negativepressure in the fluid flow path, and the controller is furtherconfigured to determine if the third indicator deviates from a thirdthreshold and in response to a determination that the third indicatordeviates from the third threshold, determine that the wound dressing iscoupled to the wound.

In some embodiments, a method for applying negative pressure to a woundis disclosed. The method can include: providing negative pressure with anegative pressure source to a wound dressing via a fluid flow path;monitoring pressure in the fluid flow path; and based at least in parton the pressure in the fluid flow path, determining that the wounddressing is coupled to a wound from one of detection of change in flowof gas in the fluid flow path, detection of change in flow of exudate inthe fluid flow path, change in vacuum level if the fluid flow path, ordetection of presence of blood in the fluid flow path; and outputting anindication that the wound dressing is coupled to the wound.

The method of the preceding paragraph can include one or more of thefollowing features: Said determining comprises determining that thewound dressing is coupled to the wound further from an activity level ofthe negative pressure source. The negative pressure source comprises apump operated by an actuator, and the activity level comprises at leastone of a pump speed, a pulse width modulation (PWM) signal configured todrive the actuator, or a current signal configured to drive theactuator. The method can further include determining a first indicatorassociated with change in the activity level over a time duration. Thefirst indicator comprises a statistical indicator. The method canfurther include performing a time series analysis to determine if thefirst indicator deviates from a first threshold and, in response todetermining that the first indicator deviates from the first threshold,determining that the wound dressing is coupled to the wound. The timeseries analysis comprises determination of a cumulative sum (Cusum) ofthe first indicator. The Cusum of the first indicators comprises anon-causal Cusum, sliding causal Cusum, or cumulative causal Cusum. Thefirst indicator comprises kurtosis of standard deviation of the activitylevel, and the first indicator is indicative of a change in flow ofexudate in the fluid flow path. The method can further includedetermining a cumulative sum (Cusum) of second indicator associated withchange in the activity level over the time duration, the secondindicator different from the first indicator. The second indicatorcomprises standard deviation of the activity level indicative of achange in a gas leak rate in the fluid flow path, and the method canfurther include determining if the second indicator deviates from asecond threshold and, in response to determining that the secondindicator deviates from the second threshold, determining that the wounddressing is coupled to the wound. The method can further includedetermining a cumulative sum (Cusum) of third indicator associated withchange in the pressure in the fluid flow path over the time duration,the third indicator different from the first and second indicators. Thethird indicator comprises mean pressure in the fluid flow pathindicative of a change in negative pressure in the fluid flow path, andthe method can further include determining if the third indicatordeviates from a third threshold and, in response to determining that thethird indicator deviates from the third threshold, determining that thewound dressing is coupled to the wound.

DETAILED DESCRIPTION

The present disclosure relates to methods and apparatuses for dressingand treating a wound with reduced pressure therapy or topical negativepressure (TNP) therapy. In particular, but without limitation,embodiments of this disclosure relate to negative pressure therapyapparatuses, methods for controlling the operation of TNP systems, andmethods of using TNP systems. The methods and apparatuses canincorporate or implement any combination of the features describedbelow.

TNP therapy can assist in the closure and healing of many forms of “hardto heal” wounds by reducing tissue oedema, encouraging blood flow andgranular tissue formation, or removing excess exudate and can reducebacterial load (and thus infection risk). In addition, TNP therapy mayallow for less disturbance of a wound leading to more rapid healing. TNPsystems can also assist in the healing of surgically closed wounds byremoving fluid or help to stabilize the tissue in the apposed positionof closure. A further beneficial use of TNP therapy can be found ingrafts and flaps where removal of excess fluid is important and closeproximity of the graft to tissue is required in order to ensure tissueviability.

As is used herein, reduced or negative pressure levels, such as −X mmHg,represent pressure levels that are below atmospheric pressure, whichtypically corresponds to 760 mmHg (or 1 atm, 29.93 inHg, 101.325 kPa,14.696 psi, etc.). Accordingly, a negative pressure value of −X mmHgreflects pressure that is X mmHg below atmospheric pressure, such as apressure of (760−X) mmHg. In addition, negative pressure that is “less”or “smaller” than −X mmHg corresponds to pressure that is closer toatmospheric pressure (e.g., −40 mmHg is less than −60 mmHg). Negativepressure that is “more” or “greater” than −X mmHg corresponds topressure that is further from atmospheric pressure (e.g., −80 mmHg ismore than −60 mmHg).

Overview

It may be difficult, in some instances, to confirm whether a negativepressure source, such as a pump, of a TNP apparatus (sometimes referredto herein as a pump assembly) is in use on a patient. A TNP apparatuscan log the usage of its negative pressure source as a function of timebetween the activation and deactivation of the negative pressure source,as well as log events such as alarms, measured pressure, or changes to atherapy program administered by the TNP apparatus. However, the timebetween the activation and deactivation and the log events may notenable the TNP apparatus to confidently determine whether the negativepressure source is activated but not coupled via a fluid flow path to awound. The TNP apparatus may, for instance, be unable to distinguishwith confidence whether the negative pressure source is being used totreat a wound or instead being used while uncoupled from a wound andsimply placed aside or in storage with the wound dressing not forming asubstantially fluid tight seal over any surface or forming the seal overa surface other than tissue of the patient (for example, the dressingmay be positioned over a table, door, etc.). Moreover, the TNP apparatusmay be used for training, tampered with in a way that impacts treatment,or it may take a long time to set up use on a patient. As a result, itmay be difficult to distinguish data collected from such uses orsituations and data collected from treatment use on the patient.

In order to accurately understand the usage of a TNP apparatus, it canbe desirable to know with greater confidence if a negative pressuresource of the TNP apparatus is in use on a patient. For example, it maybe desirable to monitor compliance of use of the TNP apparatus and thusto determine whether the TNP apparatus is being used in a complaintmanner, such as to treat a wound, or instead being used in anon-compliant matter, such as being turned on but left unconnected to awound.

Advantageously, in certain embodiments, a TNP apparatus canautomatically detect whether a negative pressure source of TNP apparatusis coupled via a fluid flow path to a wound, such as the wound cavity110. As a result, the TNP apparatus can automatically determine whetherthe TNP apparatus is in use on a patient and thus used in a compliantmanner. This automatic determination by the TNP apparatus can moreoverenable data collected by the TNP apparatus for diagnosis or complianceof the patient to be validated as resulting from therapeutic use on thepatient.

In one implementation, a TNP apparatus can analyze a magnitude ofpressure (such as by measuring raw peak-to-peak pressure readings) in aTNP system that includes the TNP apparatus to determine whether thenegative pressure source is pumping on or against a wound dressingcoupled to a wound, such as the wound cover 120 and the wound filler 130coupled to the wound cavity 110, or against its own system (for example,the negative pressure source or the wound dressing may be left uncoupledor instead may be coupled to something other than a wound like aninanimate object). When the negative pressure source may be maintainingpressure against its own system rather than against the wound dressingcoupled to the wound, the magnitude of pressure in the TNP system canrelatively quickly begin to follow a regular pattern or reach a steadystate condition because there may be no liquid moving through the TNPsystem and the TNP system may not be moving or flexing irregularly. TheTNP apparatus can accordingly determine whether the change in themagnitude of pressure in the TNP system follows an irregular pattern ora chaotic condition indicative of use of the TNP apparatus on a patientor a regular pattern or a steady state condition not indicative of useof the TNP apparatus on a patient.

Moreover, a TNP apparatus can analyze artifacts in a pressure signal todetermine whether the negative pressure source is pumping against awound dressing coupled to a wound. The artifacts can be produced bymechanical or fluidic changes in a TNP system that includes the TNPapparatus. For example, mechanical movement at a wound (for example, dueto patient's movement) coupled to a wound dressing can manifest as anartifact in the pressure signal. As another example, liquid passage inthe TNP system can manifest as an artifact in the pressure signal.Notably, some artifacts may appear to be random while other artifacts,such as from pulse or respiration, may follow a substantially periodicpattern.

Negative Pressure System

FIG. 1 illustrates an embodiment of a negative or reduced pressure woundtreatment (or TNP) system 100 comprising a wound filler 130 placedinside a wound cavity 110, the wound cavity sealed by a wound cover 120.The wound filler 130 in combination with the wound cover 120 can bereferred to as wound dressing. A single or multi lumen tube or conduit140 is connected the wound cover 120 with a pump assembly 150 configuredto supply reduced pressure. The wound cover 120 can be in fluidiccommunication with the wound cavity 110. In any of the systemembodiments disclosed herein, as in the embodiment illustrated in FIG.1, the pump assembly can be a canisterless pump assembly (meaning thatexudate is collected in the wound dressing or is transferred via tube140 for collection to another location). However, any of the pumpassembly embodiments disclosed herein can be configured to include orsupport a canister. Additionally, in any of the system embodimentsdisclosed herein, any of the pump assembly embodiments can be mounted toor supported by the dressing, or adjacent to the dressing.

The wound filler 130 can be any suitable type, such as hydrophilic orhydrophobic foam, gauze, inflatable bag, and so on. The wound filler 130can be conformable to the wound cavity 110 such that it substantiallyfills the cavity. The wound cover 120 can provide a substantially fluidimpermeable seal over the wound cavity 110. The wound cover 120 can havea top side and a bottom side, and the bottom side adhesively (or in anyother suitable manner) seals with wound cavity 110. The conduit 140 orlumen or any other conduit or lumen disclosed herein can be formed frompolyurethane, PVC, nylon, polyethylene, silicone, or any other suitablematerial.

Some embodiments of the wound cover 120 can have a port (not shown)configured to receive an end of the conduit 140. For example, the portcan be Renays Soft Port available from Smith & Nephew. In otherembodiments, the conduit 140 can otherwise pass through or under thewound cover 120 to supply reduced pressure to the wound cavity 110 so asto maintain a desired level of reduced pressure in the wound cavity. Theconduit 140 can be any suitable article configured to provide at least asubstantially sealed fluid flow pathway between the pump assembly 150and the wound cover 120, so as to supply the reduced pressure providedby the pump assembly 150 to wound cavity 110.

The wound cover 120 and the wound filler 130 can be provided as a singlearticle or an integrated single unit. In some embodiments, no woundfiller is provided and the wound cover by itself may be considered thewound dressing. The wound dressing may then be connected, via theconduit 140, to a source of negative pressure, such as the pump assembly150. The pump assembly 150 can be miniaturized and portable, althoughlarger conventional pumps such can also be used.

The wound cover 120 can be located over a wound site to be treated. Thewound cover 120 can form a substantially sealed cavity or enclosure overthe wound site. In some embodiments, the wound cover 120 can beconfigured to have a film having a high water vapor permeability toenable the evaporation of surplus fluid, and can have a superabsorbingmaterial contained therein to safely absorb wound exudate. It will beappreciated that throughout this specification reference is made to awound. In this sense it is to be understood that the term wound is to bebroadly construed and encompasses open and closed wounds in which skinis torn, cut or punctured or where trauma causes a contusion, or anyother surficial or other conditions or imperfections on the skin of apatient or otherwise that benefit from reduced pressure treatment. Awound is thus broadly defined as any damaged region of tissue wherefluid may or may not be produced. Examples of such wounds include, butare not limited to, acute wounds, chronic wounds, surgical incisions andother incisions, subacute and dehisced wounds, traumatic wounds, flapsand skin grafts, lacerations, abrasions, contusions, burns, diabeticulcers, pressure ulcers, stoma, surgical wounds, trauma and venousulcers or the like. The components of the TNP system described hereincan be particularly suited for incisional wounds that exude a smallamount of wound exudate.

Some embodiments of the system are designed to operate without the useof an exudate canister. Some embodiments can be configured to support anexudate canister. In some embodiments, configuring the pump assembly 150and tubing 140 so that the tubing 140 can be quickly and easily removedfrom the pump assembly 150 can facilitate or improve the process ofdressing or pump changes, if necessary. Any of the pump embodimentsdisclosed herein can be configured to have any suitable connectionbetween the tubing and the pump.

The pump assembly 150 can be configured to deliver negative pressure ofapproximately −80 mmHg, or between about −20 mmHg and 200 mmHg in someimplementations. Note that these pressures are relative to normalambient atmospheric pressure thus, −200 mmHg would be about 560 mmHg inpractical terms. The pressure range can be between about −40 mmHg and−150 mmHg. Alternatively a pressure range of up to −75 mmHg, up to −80mmHg or over −80 mmHg can be used. Also a pressure range of below −75mmHg can be used. Alternatively a pressure range of over approximately−100 mmHg, or even 150 mmHg, can be supplied by the pump assembly 150.

In operation, the wound filler 130 is inserted into the wound cavity 110and wound cover 120 is placed so as to seal the wound cavity 110. Thepump assembly 150 provides a source of a negative pressure to the woundcover 120, which is transmitted to the wound cavity 110 via the woundfiller 130. Fluid (e.g., wound exudate) is drawn through the conduit140, and can be stored in a canister. In some embodiments, fluid isabsorbed by the wound filler 130 or one or more absorbent layers (notshown).

Wound dressings that may be utilized with the pump assembly and otherembodiments of the present application include Renasys-F, Renasys-G,Renasys Aft and Pico Dressings available from Smith & Nephew. Furtherdescription of such wound dressings and other components of a negativepressure wound therapy system that may be used with the pump assemblyand other embodiments of the present application are found in U.S.Patent Publication Nos. 2011/0213287, 2011/0282309, 2012/0116334,2012/0136325, and 2013/0110058, which are incorporated by reference intheir entirety. In other embodiments, other suitable wound dressings canbe utilized.

FIG. 2A illustrates a front view of a pump assembly 230 and canister 220according to some embodiments. As is illustrated, the pump assembly 230and the canister are connected, thereby forming a negative pressurewound therapy device. The pump assembly 230 can be similar to or thesame as the pump assembly 150 in some embodiments.

The pump assembly 230 includes one or more indicators, such as visualindicator 202 configured to indicate alarms and visual indicator 204configured to indicate status of the TNP system. The indicators 202 and204 can be configured to alert a user, such as patient or medical careprovider, to a variety of operating or failure conditions of the system,including alerting the user to normal or proper operating conditions,pump failure, power supplied to the pump or power failure, detection ofa leak within the wound cover or flow pathway, suction blockage, or anyother similar or suitable conditions or combinations thereof. The pumpassembly 230 can comprise additional indicators. The pump assembly canuse a single indicator or multiple indicators. Any suitable indicatorcan be used such as visual, audio, tactile indicator, and so on. Theindicator 202 can be configured to signal alarm conditions, such ascanister full, power low, conduit 140 disconnected, seal broken in thewound seal 120, and so on. The indicator 202 can be configured todisplay red flashing light to draw user's attention. The indicator 204can be configured to signal status of the TNP system, such as therapydelivery is ok, leak detected, and so on. The indicator 204 can beconfigured to display one or more different colors of light, such asgreen, yellow, etc. For example, green light can be emitted when the TNPsystem is operating properly and yellow light can be emitted to indicatea warning.

The pump assembly 230 includes a display or screen 206 mounted in arecess 208 formed in a case of the pump assembly. The display 206 can bea touch screen display. The display 206 can support playback ofaudiovisual (AV) content, such as instructional videos. As explainedbelow, the display 206 can be configured to render a number of screensor graphical user interfaces (GUIs) for configuring, controlling, andmonitoring the operation of the TNP system. The pump assembly 230comprises a gripping portion 210 formed in the case of the pumpassembly. The gripping portion 210 can be configured to assist the userto hold the pump assembly 230, such as during removal of the canister220. The canister 220 can be replaced with another canister, such aswhen the canister 220 has been filled with fluid.

The pump assembly 230 includes one or more keys or buttons configured toallow the user to operate and monitor the operation of the TNP system.As is illustrated, there buttons 212 a, 212 b, and 212 c (collectivelyreferred to as buttons 212) are included. Button 212 a can be configuredas a power button to turn on/off the pump assembly 230. Button 212 b canbe configured as a play/pause button for the delivery of negativepressure therapy. For example, pressing the button 212 b can causetherapy to start, and pressing the button 212 b afterward can causetherapy to pause or end. Button 212 c can be configured to lock thedisplay 206 or the buttons 212. For instance, button 212 c can bepressed so that the user does not unintentionally alter the delivery ofthe therapy. Button 212 c can be depressed to unlock the controls. Inother embodiments, additional buttons can be used or one or more of theillustrated buttons 212 a, 212 b, or 212 c can be omitted. Multiple keypresses or sequences of key presses can be used to operate the pumpassembly 230.

The pump assembly 230 includes one or more latch recesses 222 formed inthe cover. In the illustrated embodiment, two latch recesses 222 can beformed on the sides of the pump assembly 230. The latch recesses 222 canbe configured to allow attachment and detachment of the canister 220using one or more canister latches 221. The pump assembly 230 comprisesan air outlet 224 for allowing air removed from the wound cavity 110 toescape. Air entering the pump assembly can be passed through one or moresuitable filters, such as antibacterial filters. This can maintainreusability of the pump assembly. The pump assembly 230 includes one ormore strap mounts 226 for connecting a carry strap to the pump assembly230 or for attaching a cradle. In the illustrated embodiment, two strapmounts 226 can be formed on the sides of the pump assembly 230. In someembodiments, various of these features are omitted or various additionalfeatures are added to the pump assembly 230.

The canister 220 is configured to hold fluid (e.g., exudate) removedfrom the wound cavity 110. The canister 220 includes one or more latches221 for attaching the canister to the pump assembly 230. In theillustrated embodiment, the canister 220 comprises two latches 221 onthe sides of the canister. The exterior of the canister 220 can formedfrom frosted plastic so that the canister is substantially opaque andthe contents of the canister and substantially hidden from plain view.The canister 220 comprises a gripping portion 214 formed in a case ofthe canister. The gripping portion 214 can be configured to allow theuser to hold the pump assembly 220, such as during removal of thecanister from the apparatus 230. The canister 220 includes asubstantially transparent window 216, which can also include graduationsof volume. For example, the illustrated 300 mL canister 220 includesgraduations of 50 mL, 100 mL, 150 mL, 200 mL, 250 mL, and 300 mL. Otherembodiments of the canister can hold different volume of fluid and caninclude different graduation scale. For example, the canister can be an800 mL canister. The canister 220 comprises a tubing channel 218 forconnecting to the conduit 140. In some embodiments, various of thesefeatures, such as the gripping portion 214, are omitted or variousadditional features are added to the canister 220. Any of the disclosedcanisters may include or may omit a solidifier.

FIG. 2B illustrates a rear view of the pump assembly 230 and canister220 according to some embodiments. The pump assembly 230 comprises aspeaker port 232 for producing sound. The pump assembly 230 includes afilter access door 234 with a screw for removing the access door 234,accessing, and replacing one or more filters, such as antibacterial orodor filters. The pump assembly 230 comprises a gripping portion 236formed in the case of the pump assembly. The gripping portion 236 can beconfigured to allow the user to hold the pump assembly 230, such asduring removal of the canister 220. The pump assembly 230 includes oneor more covers 238 configured to as screw covers or feet or protectorsfor placing the pump assembly 230 on a surface. The covers 230 can beformed out of rubber, silicone, or any other suitable material. The pumpassembly 230 comprises a power jack 239 for charging and recharging aninternal battery of the pump assembly. The power jack 239 can be adirect current (DC) jack. In some embodiments, the pump assembly cancomprise a disposable power source, such as batteries, so that no powerjack is needed.

The canister 220 includes one or more feet 244 for placing the canisteron a surface. The feet 244 can be formed out of rubber, silicone, or anyother suitable material and can be angled at a suitable angle so thatthe canister 220 remains stable when placed on the surface. The canister220 comprises a tube mount relief 246 configured to allow one or moretubes to exit to the front of the device. The canister 220 includes astand or kickstand 248 for supporting the canister when it is placed ona surface. As explained below, the kickstand 248 can pivot between anopened and closed position. In closed position, the kickstand 248 can belatched to the canister 220. In some embodiments, the kickstand 248 canbe made out of opaque material, such as plastic. In other embodiments,the kickstand 248 can be made out of transparent material. The kickstand248 includes a gripping portion 242 formed in the kickstand. Thegripping portion 242 can be configured to allow the user to place thekickstand 248 in the closed position. The kickstand 248 comprises a hole249 to allow the user to place the kickstand in the open position. Thehole 249 can be sized to allow the user to extend the kickstand using afinger.

FIG. 2C illustrates a view of the pump assembly 230 separated from thecanister 220 according to some embodiments. The pump assembly 230includes a vacuum attachment, connector, or inlet 252 through which avacuum pump communicates negative pressure to the canister 220. The pumpassembly aspirates fluid, such as gas, from the wound via the inlet 252.The pump assembly 230 comprises a USB access door 256 configured toallow access to one or more USB ports. In some embodiments, the USBaccess door is omitted and USB ports are accessed through the door 234.The pump assembly 230 can include additional access doors configured toallow access to additional serial, parallel, or hybrid data transferinterfaces, such as SD, Compact Disc (CD), DVD, FireWire, Thunderbolt,PCI Express, and the like. In other embodiments, one or more of theseadditional ports are accessed through the door 234.

FIG. 3A illustrates components of a negative pressure therapy system300A that includes a TNP apparatus 310 and a remote data processingsystem 320. The TNP apparatus 310 can be used to treat a wound using awound dressing that is in fluidic communication with the TNP apparatus310 via a fluid flow path. The TNP apparatus 310 can include acontroller 311, a memory device 312, a negative pressure source 313, auser interface 314, a power source 315, a pressure sensor 316, and atransceiver 317 that are configured to electrically communicate with oneanother. The power source 315 can provide power to one or morecomponents of the TNP apparatus 310. The TNP apparatus 310 can operateat the pressure levels and using control approaches as described hereinor similar to those described in U.S. Patent Publication Nos.2016/0136339 and 2016/0184496, which are incorporated by reference intheir entirety. The TNP apparatus 310 can be similar to or the same asthe pump assembly 150 in some embodiments.

The controller 311 can control operations of one or more othercomponents of the TNP apparatus 310 according at least to instructionsstored in the memory device 312. The controller 311 can, for instance,control operations of and supply of negative pressure by the negativepressure source 313. The negative pressure source 313 can include apump, such as, without limitation, a rotary diaphragm pump or otherdiaphragm pump, a piezoelectric pump, a peristaltic pump, a piston pump,a rotary vane pump, a liquid ring pump, a scroll pump, a diaphragm pumpoperated by a piezoelectric transducer, or any other suitable pump ormicropump or any combinations of the foregoing.

The user interface 314 can include one or more elements that receiveuser inputs or provide user outputs to a patient or caregiver. The oneor more elements that receive user inputs can include buttons, switches,dials, touch screens, or the like. The user interface 314 can, forexample, be used to generate and display a report or other informationreflecting data from therapy use, data from non-compliant use, or acomparison of data from therapy use versus non-compliant use. As anotherexample, the user interface 314 may receive a user input providing apatient reference number or another unique identifier, and the TNPapparatus 310 may then be activated for use by the patient and datacollected and stored as described herein may be associated with thepatient reference number for usage monitoring for a particular patient.

The pressure sensor 316 can be used to monitor pressure underneath awound dressing, such as (i) pressure in a fluid flow path connecting thenegative pressure source 313 and the wound dressing as illustrated byFIG. 3B, (ii) pressure at the wound dressing as illustrated by FIG. 3C,or (iii) pressure at or in the negative pressure source 313 asillustrated by FIG. 3D. As the negative pressure source 313 providesnegative pressure, the negative pressure source 313 may generatepressure pulses that are propagated through the fluid flow path anddetected by the pressure sensor 316. These pressure pulses may show as achange or bounce in the magnitude or frequency of a signal from thepressure sensor 316.

The controller 311 can analyze a signal output by the pressure sensor316 to determine pressure in the fluid flow path. The controller 311 mayexamine the signal using one or more approaches including time domain orfrequency domain calculations, such as with a digital signal processor.

The controller 311 or other circuitry of the TNP apparatus 310 mayprocess one or more signals output by the pressure sensor 316 byfiltering out noise and then dynamically amplifying the filtered one ormore signals. Dynamic amplification can be performed without filtering.This may enable the features described herein to be applied to smallerwounds or weaker pressure signals. For example, the amplification can beperformed by a programmable gain amplifier, which may be controlled bysoftware or hardware.

The detection of pressure by the pressure sensor 316 can, in someinstances, be enhanced by changing one or more settings of the negativepressure source 313, such as increasing or decreasing vacuum leveldelivered by the negative pressure source 313, stopping the negativepressure source 313, changing an operating speed of the negativepressure source 313, changing a cadence of the negative pressure source313, combinations of the same, or the like. The controller 311 can, forexample, automatically manage adjustment of the one or more settings.

In some implementations, the pressure sensor 316 can be used incombination with another pressure sensor so that the at least twopressure sensors that are positioned in or fluidically connected to thefluid flow path to permit differential measurement of the pressure, suchas illustrated by FIG. 3E. For example, a first pressure sensor can bepositioned upstream of the wound (such as at or near the inlet of thenegative pressure source 313C) and a second pressure sensor can bepositioned to detect pressure at or near the wound or at or near acanister. This configuration can be accomplished by incorporating, inaddition to one or more lumens forming a first fluid flow pathconnecting the negative pressure source 313 to the wound, a second fluidflow path that includes one or more lumens connecting the TNP apparatus310 to the wound and through which the second pressure sensor canmonitor pressure at or near the wound or at or near a canister. Thefirst and second fluid flow paths can be fluidically isolated from eachother. When the at least two pressure sensors are used, the rate ofchange of pressure (for example, in peak-to-peak pressure or maximumpressure) in the first and second fluid flow paths can be determined andthe difference in pressure detected between the first and secondpressure sensors can be determined. These values can be used separatelyor together to detect various operational conditions, such as leaks,blockages, canister full, presence of blood in the first fluid flow pathor the second fluid flow path, etc. In some implementations, multipleredundant pressure sensors can be provided to protect against failure ofone or more of the pressure sensors.

The transceiver 317 can be used to communicate with the data processingsystem 320 via a network 330. The transceiver 317 can, for example,transmit device usage data like alarms, measured pressure, or changes toa therapy program administered by the TNP apparatus 310 to the dataprocessing system 320. The network 330 can be a communication network,such as a wireless communications network like a cellular communicationsnetwork. The memory device 312 can be used to store the device usagedata that may be transmitted by the transceiver 317.

The data processing system 320 can, in some implementations, analyzepressure data received from the transceiver 317 to determine whether thereceived pressure data is indicative of the negative pressure source 313being in use on a patient, such as using analysis approaches asdescribed with respect to the TNP apparatus 310. The data processingsystem 320 can, for instance, generate and display a report or otherinformation reflecting data from therapy use, data from non-compliantuse, or a comparison of data from therapy use versus non-compliant use.In one example, a user of the data processing system 320 may input apatient reference number or TNP apparatus number associated with a TNPapparatus, and the data processing system 320 can then provide ordisplay data like data from therapy use or data from non-compliant usefor the patient reference number or TNP apparatus number.

FIG. 3B illustrates a negative pressure therapy system 300B thatincludes the TNP apparatus 310 of FIG. 3A, as well as a first fluid flowpath 340A, a wound dressing 350, and a wound 360. The TNP apparatus 310can be used to treat the wound 360 using the wound dressing 350 that isin fluidic communication with the negative pressure source 313 via thefirst fluid flow path 340A. In particular, FIG. 3B depicts that thepressure sensor 316 can be positioned in the first fluid flow path 340A,such as at or near an inlet of the TNP apparatus 310, to measurepressure in the first fluid flow path 340A.

FIG. 3C illustrates a negative pressure therapy system 300C that differsfrom the negative pressure therapy system 300B in that the pressuresensor 316 can instead be positioned to measure pressure at or near thewound dressing 350, such as pressure underneath the wound dressing 350when the wound dressing 350 is coupled to the wound 360.

FIG. 3D illustrates a negative pressure therapy system 300D that differsfrom the negative pressure therapy system 300B in that the pressuresensor 316 can instead be positioned to measure pressure at the negativepressure source 313. In one example, the pressure sensor 316 can be apart of and within the negative pressure source 313 to measure pressuregenerated by the negative pressure source 313. In another example, thepressure sensor 316 can be separate from the negative pressure source313 and positioned to measure pressure at or near an inlet of thenegative pressure source 313.

FIG. 3E illustrates a negative pressure therapy system 300E that differsfrom the negative pressure therapy system 300B in that the negativepressure therapy system 300E further includes a second fluid flow path340B, and the pressure sensor 316 can be a differential pressure sensoror include two pressure sensors. If the pressure sensor 316 may includethe two pressure sensors, one of the two pressure sensors of thepressure sensor 316 can be positioned in the first fluid flow path 340Ato measure pressure in the first fluid flow path 340A, and the other ofthe two pressure sensors the pressure sensor 316 can be positioned inthe second fluid flow path 340B to measure pressure in the second fluidflow path 340B. If the pressure sensor 316 may be the differentialpressure sensor, the pressure sensor 316 can be fluidically connected tothe first fluid flow path 340A and the second fluid flow path 340B. Thefirst fluid flow path 340A can thus be used by the negative pressuresource 313 to provide negative pressure to the wound dressing 350, andthe second fluid flow path 340B can be used primarily by the pressuresensor 316 to measure pressure at or near the wound dressing 350, suchas under the wound dressing 360. The pressure sensor 316 can thereby beused by the TNP apparatus 310 to perform differential measurement ofpressure between pressure supplied by the negative pressure source 313and pressure at or near the wound dressing 350.

FIG. 3F illustrates a negative pressure therapy system 300F that differsfrom the negative pressure therapy system 300B in that the negativepressure therapy system 300F can further include an additional pressuresensor 370 positioned to measure pressure at or near the wound dressing350, such as pressure underneath the wound dressing 350 when the wounddressing 350 is coupled to the wound 360. The additional pressure sensor370 can generate and output a signal to the TNP apparatus 310 responsiveto the pressure measured at the wound dressing 350. The pressure sensor316 and the additional pressure sensor 370 can thus be used by the TNPapparatus 310 to perform differential measurement of pressure betweenpressure supplied by the negative pressure source 313 and pressure at ornear the wound dressing 350.

FIG. 3G illustrates a negative pressure therapy system 300G that differsfrom the negative pressure therapy system 300B in that a canister 380can be coupled between the negative pressure source 313 and the wounddressing 350 in the first fluid flow path 340A. The canister 380 cancollect exudate removed from the wound 360. The examples of FIGS. 3C-3Fcan be similarly modified to also include the canister 380, in someimplementations.

FIG. 4 illustrates a negative pressure therapy system 400 that includesa TNP apparatus 410 and sensors 420A, 420B, . . . , 420N. The sensors420A, 420B, . . . , 420N can advantageously be used, in certainembodiments, to confirm coupling to or use of the TNP apparatus 410 on apatient. The TNP apparatus 410 can be similar to or the same as the TNPapparatus 310 in some embodiments. One of the sensors 420A, 420B, . . ., 420N can be similar to or the same as the pressure sensor 316 in someembodiments. One of the sensors 420A, 420B, . . . , 420N can be similarto or the same as the pressure sensor 370 in some embodiments.

The sensors 420A, 420B, . . . , 420N can be respectively detecting fromcontact sites 430A, 430B, . . . , 430N of the patient or responsive tothe patient. The sensor 420A can, for instance, be detecting from thecontact site 430A, and the sensor 420B can be detecting from the contactsite 430B while the sensor 420N can be detecting from the contact site430N. The contact sites 430A, 430B, . . . , 430N can include tissuesites of the patient (for instance, an internal or external tissue ofthe patient at a wound, a limb, or a head of the patient), itemsattached to the patient (for instance, clothing or jewelry), or part ofthe TNP apparatus 410 or a related component like a canister. One ormore of the sensors 420A, 420B, . . . , 420N may be incorporated as partof the wound dressing or configured to couple to the wound dressing.

The sensors 420A, 420B, . . . , 420N can include, for example, one ormore of a pressure sensor, an acoustic sensor, a chemical sensor, anelectric current sensor, electric potential sensor, an impedance sensor,a magnetic sensor, an optical sensor, a color sensor, a pressure sensor,a piezoelectric sensor, a thermometer, a thermal sensor, a proximitysensor, a biosensor, a strain gauge, combinations of the same, or thelike. The sensors 420A, 420B, . . . , 420N can be the same sensorsplaced to detect at different locations or different sensors in someimplementations.

Each of the sensors 420A, 420B, . . . , 420N can transmit, via wirelessor wired communication, one or more signals responsive to acorresponding monitored one of the contact sites 430A, 430B, . . . ,430N to the TNP apparatus 410. The one or more signals can, forinstance, be responsive to a physiological condition of the patient ormovement by the patient. In turn, the TNP apparatus 410 can process theone or more signals to determine whether the one or more signals fromtwo or more of the sensors 420A, 420B, . . . , 420N indicate that theTNP apparatus 410 or related component like a wound dressing is coupledto the patient or in compliant use on the patient. The TNP apparatus 410can, for example, determine whether each or at least a subset of two ormore of the sensors 420A, 420B, . . . , 420N provide physiologicallyacceptable signals (for example, signals responsive to patient activitylike patient respiration, pulse, or motion) to the TNP apparatus 410that indicate successful coupling to or association of the TNP apparatus410 with the patient.

Wound Coupling Detection

FIG. 5 illustrates a wound coupling detection process 500 performable bya device, such as the pump assembly 150 of FIG. 1, the pump assembly 230of FIG. 2A-C, the TNP apparatus 310 of FIG. 3A, or other pump assemblieslike those described in U.S. Patent Publication Nos. 2016/0136339 and2016/0184496 that were previously incorporated herein by reference intheir entireties. For convenience, the wound coupling detection process500 is described in the context of the TNP apparatus 310 of FIG. 3A, butmay instead be implemented in other systems described herein or by othersystems not shown.

The wound coupling detection process 500 can enable the TNP apparatus310 to automatically determine whether a wound dressing coupled to theTNP apparatus 310 is coupled to a wound of a patient. The TNP apparatus310 can advantageously, in certain embodiments, output a firstindication when the wound dressing is determined to be coupled to awound or a second indication different from the first indication whenthe wound dressing is determined not to be coupled to a wound.

At block 502, the process 500 can receive pressure data. For example,the controller 311 can receive pressure data indicative of a magnitudeof pressure measured in a fluid flow path coupling the negative pressuresource 313 to a wound dressing. The pressure can be measured, forinstance, by the pressure sensor 316 using measurement approaches asdescribed herein or in U.S. Patent Publication Nos. 2016/0136339 and2016/0184496, which were previously incorporated herein by reference intheir entireties. The pressure sensor 316 can communicate informationvia a wire or wirelessly to the controller 311. In certainimplementations, the pressure sensor 316 can be positioned at or nearthe wound and wirelessly communicate information to the controller 311.In some embodiments, pressure sensor data includes one or moremagnitudes of pressure measured over a duration of time, such as 0.5seconds, 1 second, 3 seconds, and the like.

At block 504, the process 500 can determine whether a dressing iscoupled to a wound. For instance, the controller 311 can determine fromthe pressure data, such as from a change in the magnitude over time,whether the wound dressing is coupled to a wound of a patient.

In one example, the controller 311 can compare a measure of theirregularity of the change in the magnitude over time to one or morethresholds to determine whether wound dressing is coupled to the wound(and in some instances, perform the comparison multiple times to preventfalse positives due to errant pressure readings, noise, and the like).The measure of the irregularity can be responsive to the change in themagnitude over a duration of at least 1 second, 10 seconds, 30 seconds,1 minute, or 5 minutes. The controller 311 can perform a statisticaloperation, a trending operation, a filtering operation, a cumulativesummation operation, or a low-pass filtering operation on the magnitudeover time to generate the measure of irregularity. The controller 311can determine that the wound dressing is coupled to the wound inresponse to determining that the measure of irregularity satisfies athreshold corresponding to the chaotic condition or does not satisfy athreshold corresponding to the steady state condition. On the otherhand, the controller 311 can determine that the wound dressing is notcoupled to the wound in response to determining that the measure ofirregularity does not satisfy the threshold corresponding to the chaoticcondition or satisfies the threshold corresponding to the steady statecondition. The one or more thresholds to which the measure of theirregularity is compared, moreover, can vary over time (for example,automatically adjust as the patient heals) or be set responsive tooperating conditions for the TNP apparatus 310 (for example, adjust tobecome more or less sensitive to background noise) or health needs ofthe patient (for example, adjust depending on a size of a wound, genderof the patient, or age of the patient).

In yet another example, the controller 311 can compare the magnitudeover time to one or more pressure patterns, such as one stored in thememory device 312, to determine whether the wound dressing is coupled tothe wound. One pressure pattern, for instance, can be indicative ofpressure in the fluid flow path when the wound dressing is coupled tothe wound, and another different pressure pattern can be indicative ofpressure in the fluid flow path when the wound dressing is not coupledto the wound. The degree of similarity of the magnitude over timerelative to the one or more pressure patterns can be used to assign themagnitude over time as reflecting either the wound dressing is or is notcoupled to the wound.

At block 506, the process 500 can output a first indication. Forexample, in response to determining that the wound dressing is coupledto the wound, the controller 311 can output a first indicationindicative of the wound dressing being coupled to the wound. The firstindication can denote compliant usage of the TNP apparatus 310 in someinstances. The first indication can be output, for example, by one ormore of: outputting the first indication for storage in the memorydevice 312, transmitting the first indication to the data processingsystem 320 via the transceiver 317, outputting the first indication forpresentation to a user via the user interface 314, or storing the firstindication in association with device usage data of the TNP apparatus310. The outputting of the first indication can additionally controloperations of the TNP apparatus 310, such as to enable continuedactivation of the negative pressure source 313.

At block 508, the process 500 can output a second indication. Forexample, in response to determining that the wound dressing is notcoupled to the wound, the controller 311 can output a second indicationindicative of the wound dressing not being coupled to the wound. Thesecond indication can denote non-compliant usage of the TNP apparatus310 in some instances. The second indication can be output, for example,by one or more of: outputting the second indication for storage in thememory device 312, transmitting the second indication to the dataprocessing system 320 via the transceiver 317, outputting the secondindication for presentation to a user via the user interface 314, orstoring the second indication in association with device usage data ofthe TNP apparatus 310. The outputting of the second indication canadditionally control operations of the TNP apparatus 310, such as tocause deactivation of the negative pressure source 313 because the TNPapparatus 310 may be being used in a non-compliant manner.

The process 500 can examine data from another sensor as described, forinstance, with respect to FIG. 4 to provide additional information orconfidence as to whether the TNP apparatus 310 may be being used in acompliant or non-compliant manner. For example, if another sensorassociated with the TNP apparatus 310 detects a signal reflecting apulse or respiration of a patient, the TNP apparatus 310 may havefurther confidence and information that the TNP apparatus 310 is beingused in a compliant manner rather than a non-compliant manner.

FIG. 6 illustrates an example pressure versus time curve 600 for a TNPsystem in which a negative pressure source of a TNP apparatus, such theTNP apparatus 310, is in use on a wound of a patient. As can be seenfrom FIG. 6, once the negative pressure source has been activated for aperiod of time, at time T₁ the magnitude of pressure in the fluid flowpath can generally fluctuate around a target pressure level. Themagnitude of pressure in the fluid flow path, however, can besubstantially chaotic and unpredictable from time T₁ to T₂ for a numberof reasons. The patient can be continuously moving due to physicaladjustments of the position, breathing, or pulse, thus affecting, forinstance, the geometry of the wound, the dressing seal, etc. As aresult, the volume of the wound may continuously be undergoing minorchanges which can result in changes in the magnitude of pressure.Further, the wound can produce exudate, which upon entering the fluidflow path can cause a gas volume to decrease. Because the gas volume canrepresent the compressible volume in the system, this compressiblevolume can act as a damper to pressure spikes created by the negativepressure source and movement of the patient so that the pressures spikesbecome increasingly large due to reduced damping. In addition, liquidcan leave the wound dressing and travel up through the fluid flow pathin slugs, and these slugs can affect (for example, increase in magnitudeor frequency) the pressure spikes. Overall, this can result is arelatively significant amount of noise in the pressure readings. Themagnitude of pressure depicted by FIG. 6 may thus be reflective of achaotic condition from time T₁ to T₂ rather than a steady statecondition. In addition or alternatively, other characteristics ofpressure, such as frequency, can be monitored for changes. For example,from time T₁ to T₂, frequency of the pressure signal is smaller in overthe time duration 612 than the time duration 614.

In one implementation, the TNP apparatus 310 can monitor the noisedescribed in the preceding paragraph to determine whether the negativepressure source is connected to a patient. Thus, the TNP apparatus 11can, for example, flag usage data and logging of events as either (i)patient data or (ii) device misuse. The TNP apparatus 310 can, in someinstances, use statistical techniques trending techniques or filteringtechniques, such as cumulative sum (Cusum) or low-pass filtering, todetermine if the pressure readings may be in steady state (not attachedto a wound) or chaotic (attached to a wound).

FIG. 7 illustrates an example pressure versus time curve 700 for a TNPsystem in which a negative pressure source of a TNP apparatus, such theTNP apparatus 310, is not in use on a wound of a patient. As can be seenfrom FIG. 7, once the negative pressure source has been activated for aperiod of time, at time T₃ the magnitude of pressure in the fluid flowpath can generally fluctuate around a target pressure level. Thefrequency can generally fluctuate around a particular frequency value.The magnitude of pressure in the fluid flow path, however, can be lesschaotic and more predictable (such as from time T₃ to T₄) than when theTNP apparatus is in use on the wound, for at least the reasons describedin the preceding two paragraphs as well as other reasons describedherein. The magnitude of pressure depicted by FIG. 7 may thus bereflective of a steady state condition from time T₃ to T₄ rather than achaotic condition.

From comparing pressure characteristic depicted from time T₁ to T₂ inFIG. 6 and from time T₃ to T₄ in FIG. 7, the following features can benoted. The characteristics of pressure from time T₁ to T₂ in FIG. 6 canhave one or more of a greater pressure magnitude variation, morepressure frequency variation over time, higher pressure magnitudecomponents (such as, spikes), or greater randomness than the magnitudeor frequency of pressure as compared to pressure variations over time T₃to T₄ in FIG. 7.

In some embodiments, time series analysis algorithms such AutoRegressive Integrated Moving Average (ARIMA), Generalized AutoregressiveConditional Heteroskedasticity (GARCH), or Cusum (or cumulative sum) canbe used to detect use on a wound of a patient. Cusum can be defined asthe running sum of the difference between each sample and the mean(e.g., in the absence of change, Cusum is zero). Cusum can be used totrack variations in the underlying variable.

Cusum can be determined in a number of ways. In certain implementations,non-causal Cusum uses the mean calculated from the entire duration of aninput signal, which requires knowledge of all samples before thedifference from the mean can be calculated. Non-causal Cusum may not besuitable for real-time monitoring and detection and classificationunless an estimate of the mean from prior analysis can be used.Non-causal Cusum can starts and end with a value of zero.

The sliding causal Cusum can be determined using a sliding window toestimate the mean. Initial step change can yield the first departurefrom zero, rather than resulting in a change of gradient as in thenon-causal Cusum. Sliding causal Cusum can produce data within durationsof time that are shorter than with non-causal Cusum. Sliding causalCusum may allow tighter bounds to be used to detect changes and may beless prone to rounding and rollover errors (e.g., numerical errors thatmay result from use of longer sequences of data).

The cumulative causal Cusum determination may use all preceding samplesfrom the start of a time duration to the current sample to estimate themean for the current sample in some embodiments. This version of Cusumcan be a compromise between the foregoing two versions, and may besmoother than sliding causal Cusum but not ending at a zero value.

A TNP apparatus can, for example, be connected to a wound model and oneor more sensors can be used to detect one or more of the parameters inTable 1. These parameters can include pressure measurements, level ofactivity measurements, and the like obtained during operation of thenegative pressure wound therapy system. In some embodiments, the levelof activity can include one or more parameters of an actuator (e.g.,motor) of the negative pressure source (e.g., pump), such as current (orvoltage) of a motor drive signal, PWM signal, and motor speed. Theapparatus can be operated under the conditions of changing one of vacuumlevel provided by the negative pressure source, rate of water removedfrom the wound, rate of exudate removed from the wound, rate of bloodremoved from the wound, or gas (e.g., air) leak rate in the fluid flowpath while maintaining the other parameters constant. This way,operational parameters can be determined, statistics can be computed andanalyzed (e.g., by using Cusum analysis), and the most appropriatestatistic(s) for detecting use on a wound of a patient can be selected.In addition, in some embodiments, statistical properties of one or moreof the statistics in Table 1 are calculated. These statisticalproperties can include one or more of mean, standard deviation, skewness(third statistical moment), kurtosis (fourth statistical moment),minimum, and maximum.

TABLE 1 Input signals and statistics Input Signal Statistic VacuumPressure Raw Vacuum Pressure Mean Vacuum Pressure Standard DeviationVacuum Pressure Peak to Peak Current Raw Current Mean Current StandardDeviation Current Peak to Peak PWM Raw PWM Mean PWM Standard DeviationPWM Peak to Peak Impulse (Motor Speed) Raw Impulse (Motor Speed) MeanImpulse (Motor Speed) Standard Deviation Impulse (Motor Speed) Peak toPeak Tick Rate (Motor Speed) Raw

Using correlation and fitness analysis is described, for instance, inInternational Patent Application No. PCT/US2017/017538 titled “SYSTEMSAND METHODS FOR DETECTING OPERATIONAL CONDITIONS OF REDUCED PRESSURETHERAPY,” filed on Feb. 10, 2017, the entirety of which is incorporatedby reference, the following statistics can be selected for detection andclassification of one or more operational conditions of a TNP apparatus:

TABLE 2 Statistics used for detection and classification OperationalCondition Statistic Vacuum level Mean of the raw vacuum (e.g., 802) Gasleak rate Standard deviation of the rolling mean of motor current (e.g.,804) Water/Exudate Kurtosis of the rolling standard deviation of pumpspeed rate (e.g., 806) Blood rate Standard deviation of the rollingstandard deviation of the motor current (e.g., 808)

For example, in the graphs illustrated in FIGS. 8-10, a TNP apparatuswas operated initially in steady-state and thereafter one of theoperational parameters or variables was changed. In FIG. 8, theintensity of gas (e.g., air) leak in the fluid flow path has beenchanged (e.g., from 60 sccm to 180 sccm at around 5 seconds) andcollected and analyzed data is used to perform detection of an abruptincrease in the leak rate. In FIG. 9, flow rate of fluid (e.g., exudate)has been changed (e.g., bolus of fluid introduced into the fluid flowpath at around 5 seconds) and collected and analyzed data is used toperform detection of change in the fluid flow rate. In FIG. 10, vacuumlevel produced by the negative pressure source has been changed (e.g.,from −80 mmHg to −120 mmHg at around 18 seconds) and collected andanalyzed data is used to perform detection of change in vacuum pressurein the fluid flow path.

FIG. 8 illustrates detection 800 of a gas leak when exudate is beingaspirated from a wound according to some embodiments. Four plots 800 a,800 b, 800 c, and 800 d are illustrated corresponding to, respectively,raw (or unprocessed) values of the statistics in Table 2 and non-causalCusum, sliding causal Cusum, and cumulative causal Cusum of thestatistics in Table 2. In plots 800 a-d, curves 802 represent raw andCusum values of mean of raw vacuum, curves 804 represent raw and Cusumvalues of standard deviation of the rolling mean of motor current,curves 806 represent raw and Cusum values of kurtosis of rollingstandard deviation of pump speed, and curves 808 represent standarddeviation of rolling standard deviation of motor current. X-axes in theplots 800 a-d corresponds to time duration (e.g., 60 seconds). Y-axis inplot 800 a represents logarithmic scale (to normalized different rawvalues of the statistics), and y-axes in plots 800 b-d are linearlyscaled (or normalized) so that Cusum values are in the range (−1.0,1.0). Plots 800 a-d capture data corresponding to a change (e.g.,increase) in the gas leak rate (e.g., from 60 sccm to 180 sccm at around5 seconds).

FIG. 9 illustrates detection 900 of a change in fluid rate when exudateis being aspirated from a wound according to some embodiments. Fourplots 900 a-d are illustrated corresponding to, respectively, raw (orunprocessed) values of the statistics in Table 2 (labeled 802, 804, 806,and 808) and non-causal Cusum, sliding causal Cusum, and cumulativecausal Cusum of the statistics. Plots 800 a-d capture data correspondingto a change (e.g., increase) in exudate flow rate due to bolus ofexudate being released into the fluid flow path (e.g., at around 5seconds).

FIG. 10 illustrates detection 1000 of a change in vacuum level whenexudate is being aspirated from a wound according to some embodiments.Four plots 1000 a-d are illustrated corresponding to, respectively, raw(or unprocessed) values of the statistics in Table 2 (labeled 802, 804,806, and 808) and non-causal Cusum, sliding causal Cusum, and cumulativecausal Cusum of the statistics. Plots 1000 a-d capture datacorresponding to a change (e.g., increase) in vacuum level provided bythe pump (e.g., from −80 mmHg to −120 mmHg at around 18 seconds).

In certain implementations, as described in International PatentApplication No. PCT/US2017/017538, similar plots can be obtained whenanother type of fluid, such as water or blood, is introduced into thefluid flow path.

Detection of one or more operational conditions described herein canmoreover be used for detection of use on a wound of a patient. Forexample, with reference to FIG. 8, various Cusums (non-causal, slidingcausal, and cumulative causal) for the standard deviation of the rollingmean of motor current (804) are responsive to the increase in the gasleak around 5 seconds. Non-causal Cusum illustrated in 800 b sharplyincreases between about 5 and 8 seconds, flattens out between about 9and 30 seconds, and then gradually decreases after about 30 seconds.Sliding causal Cusum illustrated in 800 c stays relatively flat betweenabout 5 and 7 seconds, sharply decreases at 9 seconds, and then staysrelatively flat. Cumulative causal Cusum illustrated in 800 c staysrelatively flat between about 5 and 8 seconds and linearly ormonotonically decreases thereafter. Any of such patterns, includingsharp, gradual, or linear changes (increases or decreases), can becompared to one or more thresholds to detect changes in the gas leakrate. Detection of such changes in the gas leak rate can be indicativeof use on a wound of a patient.

As another example, with reference to FIG. 9, various Cusums(non-causal, sliding causal, and cumulative causal) for the kurtosis ofthe rolling standard deviation of pump speed (806) are responsive to theincrease in the exudate flow rate at around 5 seconds. As illustrated inplots 900 b-d, curve 806 is substantially periodic after about 6 secondsand reaches several distinctive peaks around 20, 25, and 35 seconds.Such patterns indicating change in the exudate flow rate can bedetected, by, for example, comparison to one or more thresholds, and canbe used to provide indication of use on a wound of a patient.

As yet another example, with reference to FIG. 10, various Cusums(non-causal, sliding causal, and cumulative causal) for the mean vacuum(802) are responsive to the increase in the vacuum level at around 18seconds. Non-causal Cusum illustrated in 1000 b linearly ormonotonically increases after about 18 seconds. Cumulative causal Cusumillustrated in 1000 c stays linearly or monotonically increases afterabout 18 seconds. Any of such patterns, including linear changes(increases or decreases), can be compared to one or more thresholds todetect changes in the vacuum level. Detection of such changes in the gasleak rate can be indicative of use on a wound of a patient.

Presence of blood or change in flow rate of blood can detected based on,for example, the standard deviation of the rolling standard deviation ofthe motor current (808) as described in International Patent ApplicationNo. PCT/US2017/017538. Detection of any one or more of changes in thegas leak rate, vacuum level, exudate flow rate, or blood flow rate canbe used to provide indication of use on a wound of a patient.

Other Variations

In some embodiments, an apparatus for detecting compliant andnon-compliant use of a negative pressure wound therapy device isdisclosed. The apparatus can include a memory device and a processor.The memory device can store pressure data indicative of a magnitude ofpressure over time in a fluid flow path connecting a negative pressuresource and a wound dressing. The processor can be in communication withthe memory device. The processor can: determine from a change in themagnitude over time whether the wound dressing was coupled to a woundwhen the negative pressure source provided negative pressure to thewound dressing, output a first indication in response determining thatthe wound dressing was coupled to the wound when the negative pressuresource provided negative pressure to the wound dressing, and output asecond indication different from the first indication in responsedetermining that the wound dressing was not coupled to the wound whenthe negative pressure source provided negative pressure to the wounddressing.

The apparatus of the preceding paragraph can include one or more of thefollowing features: The apparatus can further include a receiverconfigured to receive the pressure data via a communication network. Thecommunication network can be a wireless communication network. Theprocessor can compare a measure of irregularity of the change in themagnitude over time to a threshold to determine whether the wounddressing was coupled to the wound. The processor can: perform astatistical operation, a trending operation, a filtering operation, acumulative summation operation, or a low-pass filtering operation on themagnitude over time to generate an output value; and determine that thewound dressing was coupled to the wound in response to determining thatthe output value is more indicative of a chaotic condition than a steadystate condition. The processor can compare the magnitude over time to apressure pattern to determine whether the wound dressing was coupled tothe wound. The processor can output the second indication by outputtingthe second indication for presentation to a user on a graphic userinterface. The processor can output the second indication by generatingand transmitting an alert for presentation to a user on a graphic userinterface. The processor can store, in the memory device, device usagedata in association with the first indication to denote that the deviceusage data is associated with a compliant use of the negative pressuresource. The processor can store, in the memory device, device usage datain association with the second indication to denote that the deviceusage data is associated with a non-compliant use of the negativepressure source.

A method of operating or manufacturing the apparatus of any of thepreceding two paragraphs is disclosed.

Any value of a threshold, limit, duration, etc. provided herein is notintended to be absolute and, thereby, can be approximate. In addition,any threshold, limit, duration, etc. provided herein can be fixed orvaried either automatically or by a user. Furthermore, as is used hereinrelative terminology such as exceeds, greater than, less than, etc. inrelation to a reference value is intended to also encompass being equalto the reference value. For example, exceeding a reference value that ispositive can encompass being equal to or greater than the referencevalue. In addition, as is used herein relative terminology such asexceeds, greater than, less than, etc. in relation to a reference valueis intended to also encompass an inverse of the disclosed relationship,such as below, less than, greater than, etc. in relations to thereference value. Moreover, although blocks of the various processes maybe described in terms of determining whether a value meets or does notmeet a particular threshold, the blocks can be similarly understood, forexample, in terms of a value (i) being below or above a threshold or(ii) satisfying or not satisfying a threshold.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example describedherein unless incompatible therewith. All of the features disclosed inthis specification (including any accompanying claims, abstract anddrawings), and/or all of the steps of any method or process sodisclosed, may be combined in any combination, except combinations whereat least some of such features and/or steps are mutually exclusive. Theprotection is not restricted to the details of any foregoingembodiments. The protection extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of protection. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms. Furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made. Those skilled in the art willappreciate that in some embodiments, the actual steps taken in theprocesses illustrated and/or disclosed may differ from those shown inthe figures. Depending on the embodiment, certain of the steps describedabove may be removed, others may be added. For example, the actual stepsand/or order of steps taken in the disclosed processes may differ fromthose shown in the figure. Depending on the embodiment, certain of thesteps described above may be removed, others may be added. For instance,the various components illustrated in the figures may be implemented assoftware and/or firmware on a processor, controller, ASIC, FPGA, and/ordedicated hardware. Hardware components, such as processors, ASICs,FPGAs, and the like, can include logic circuitry. Furthermore, thefeatures and attributes of the specific embodiments disclosed above maybe combined in different ways to form additional embodiments, all ofwhich fall within the scope of the present disclosure.

User interface screens illustrated and described herein can includeadditional and/or alternative components. These components can includemenus, lists, buttons, text boxes, labels, radio buttons, scroll bars,sliders, checkboxes, combo boxes, status bars, dialog boxes, windows,and the like. User interface screens can include additional and/oralternative information. Components can be arranged, grouped, displayedin any suitable order.

Although the present disclosure includes certain embodiments, examplesand applications, it will be understood by those skilled in the art thatthe present disclosure extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses and obviousmodifications and equivalents thereof, including embodiments which donot provide all of the features and advantages set forth herein.Accordingly, the scope of the present disclosure is not intended to belimited by the specific disclosures of preferred embodiments herein, andmay be defined by claims as presented herein or as presented in thefuture.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, or steps are in anyway required for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements, and/or steps are includedor are to be performed in any particular embodiment. The terms“comprising,” “including,” “having,” and the like are synonymous and areused inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list.Further, the term “each,” as used herein, in addition to having itsordinary meaning, can mean any subset of a set of elements to which theterm “each” is applied.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than 10% of, within less than 5% of, within less than 1% of, withinless than 0.1% of, and within less than 0.01% of the stated amount. Asanother example, in certain embodiments, the terms “generally parallel”and “substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by less than or equal to 15 degrees,10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

1-53. (canceled)
 54. An apparatus for applying negative pressure to awound, the apparatus comprising: a negative pressure source configuredto couple via a fluid flow path to a wound dressing and provide negativepressure to the wound dressing; a sensor configured to monitor pressurein the fluid flow path; and a controller configured to: determine thatthe wound dressing is coupled to a wound from a change in a magnitude ofpressure in the fluid flow path over a time duration being indicative ofa chaotic condition while the negative pressure source maintainsnegative pressure in the fluid flow path within a target pressure range,output a first indication denoting that the wound dressing is coupled tothe wound, determine that the wound dressing is not coupled to the woundfrom the change in the magnitude of pressure in the fluid flow path overthe time duration being indicative of a steady state condition while thenegative pressure source maintains negative pressure in the fluid flowpath within the target pressure range, and output a second indicationdifferent from the first indication denoting that the wound dressing isnot coupled to the wound.
 55. The apparatus of claim 54, wherein thecontroller is further configured to: in response to the determinationthat the wound dressing is coupled to the wound, store, in a memorydevice, device usage data indicating a compliant use of the negativepressure source.
 56. The apparatus of claim 54, wherein the controlleris further configured to: in response to the determination that thewound dressing is not coupled to the wound, store, in a memory device,device usage data indicating a misuse use of the negative pressuresource.
 57. The apparatus of claim 56, wherein the device usage datacomprises one or more of a pressure level, an alarm, an exudate level,an event log, or a therapy duration.
 58. The apparatus of claim 54,wherein the controller is further configured to compare a measure ofirregularity of the change in the magnitude over the time duration to athreshold to determine whether the change in the magnitude over the timeduration is indicative of the steady state condition.
 59. The apparatusof claim 58, wherein the measure of irregularity is responsive to thechange in the magnitude over the time duration of at least 1 second, 10seconds, 30 seconds, 1 minute, or 5 minutes.
 60. The apparatus of claim54, wherein the controller is further configured to: perform astatistical operation, a trending operation, a filtering operation, acumulative summation operation, or a low-pass filtering operation on themagnitude over the time duration to generate an output value; anddetermine that the change in the magnitude over the time duration isindicative of the steady state condition in response to a determinationthat the output value is indicative of the steady state condition. 61.The apparatus of claim 54, wherein the controller is configured todetermine that the change in the magnitude over the time duration isindicative of the steady state condition from a time domainrepresentation of the magnitude over the time duration and a frequencydomain representation of the magnitude over the time duration.
 62. Theapparatus of claim 54, wherein the controller is further configured tocompare the magnitude over the time duration to a pressure pattern todetermine whether the change in the magnitude over the time duration isindicative of the steady state condition.
 63. The apparatus of claim 62,wherein the pressure pattern is indicative of pressure in the fluid flowpath when the wound dressing is coupled to the wound while the negativepressure source maintains negative pressure in the fluid flow pathwithin the target pressure range.
 64. The apparatus of claim 62, whereinthe pressure pattern is indicative of pressure in the fluid flow pathwhen the wound dressing is not coupled to the wound while the negativepressure source maintains negative pressure in the fluid flow pathwithin the target pressure range.
 65. The apparatus of claim 54, whereinthe first indication denotes a compliant use of the negative pressuresource, and the second indication denotes a non-compliant use of thenegative pressure source.
 66. The apparatus of claim 54, wherein thecontroller is further configured to: output the first indication forstorage in a memory device, or output the second indication for storagein the memory device.
 67. The apparatus of claim 54, wherein thecontroller is further configured to: output the first indication bycausing a transmitter to transmit the first indication to a computingdevice via a communication network, or output the second indication bycausing the transmitter to transmit the second indication to thecomputing device via the communication network.
 68. The apparatus ofclaim 54, wherein the controller is further configured to: output thefirst indication for presentation to a user, or output the secondindication for presentation to the user.
 69. The apparatus of claim 54,wherein the fluid flow path comprises at least one lumen.
 70. Theapparatus of claim 54, wherein the fluid flow path comprises a pluralityof lumens.
 71. The apparatus of claim 54, wherein the controller isconfigured to activate and deactivate the negative pressure sourceresponsive to the first indication or the second indication.
 72. Theapparatus of claim 54, wherein the negative pressure source isconfigured to perform negative pressure therapy when the magnitude overthe time duration is maintained within the target pressure range.
 73. Amethod of operating a negative pressure wound therapy apparatus, themethod comprising: providing negative pressure to a wound dressing via afluid flow path using a negative pressure source; monitoring with asensor pressure in the fluid flow path; determining whether the wounddressing is not coupled to a wound from a change in a magnitude ofpressure in the fluid flow path over a time duration being indicative ofa steady state condition while maintaining negative pressure in thefluid flow path within a target pressure range; in response todetermining that the wound dressing is coupled to the wound from thechange in the magnitude over the time duration, outputting a firstindication denoting that the wound dressing is coupled to the wound; andin response to determining that the wound dressing is not coupled to thewound from the change in the magnitude over the time duration,outputting a second indication different from the first indicationdenoting that the wound dressing is not coupled to the wound.
 74. Themethod of claim 73, further comprising storing, in a memory device,device usage data associated with a compliant use of the negativepressure wound therapy apparatus in response to determining the wounddressing is coupled to the wound.
 75. The method of claim 74, whereinthe device usage data comprises one or more of a pressure level, analarm, an exudate level, an event log, or a therapy duration.
 76. Themethod of claim 73, further comprising storing, in a memory device,device usage data associated with a misuse use of the negative pressurewound therapy apparatus in response to determining the wound dressing isnot coupled to the wound.
 77. The method of claim 73, wherein saiddetermining comprises comparing a measure of irregularity of the changein the magnitude over the time duration to a threshold.
 78. The methodof claim 77, wherein the measure of irregularity is responsive to thechange in the magnitude over the time duration of at least 1 second, 10seconds, 30 seconds, 1 minute, or 5 minutes.
 79. The method of claim 73,further comprising performing a statistical operation, a trendingoperation, a filtering operation, a cumulative summation operation, or alow-pass filtering operation on the magnitude over time to generate anoutput value, wherein said determining comprises determining whether thechange in the magnitude over the time duration is indicative of thesteady state condition in response to determining that the output valueis indicative of the steady state condition.
 80. The method of claim 73,further comprising comparing the magnitude over the time duration to apressure pattern to determine whether the change in the magnitude overthe time duration is indicative of the steady state condition.
 81. Anapparatus for applying negative pressure to a wound, the apparatuscomprising: a negative pressure source configured to couple via a fluidflow path to a wound dressing and provide negative pressure to the wounddressing; a sensor configured to monitor pressure in the fluid flowpath; and a controller configured to: based at least in part on thepressure in the fluid flow path, determine that the wound dressing iscoupled to a wound based on at least one of detection of change in flowof gas in the fluid flow path, detection of change in flow of exudate inthe fluid flow path, change in vacuum level if the fluid flow path, ordetection of presence of blood in the fluid flow path, and output anindication that the wound dressing is coupled to the wound.
 82. A methodfor applying negative pressure to a wound, the method comprising:providing negative pressure with a negative pressure source to a wounddressing via a fluid flow path; monitoring pressure in the fluid flowpath; based at least in part on the pressure in the fluid flow path,determining that the wound dressing is coupled to a wound from one ofdetection of change in flow of gas in the fluid flow path, detection ofchange in flow of exudate in the fluid flow path, change in vacuum levelif the fluid flow path, or detection of presence of blood in the fluidflow path; and outputting an indication that the wound dressing iscoupled to the wound.